Getting more efficiency out of a ZX2. Small list of mods and driving tips for it.

So a few things I have learned from this car after I bought it is the following:

- they are light
- they make decent power for what they are
- the engine is very efficient
- ford restricted them a LOT.
- decent room for modification

Now, when I initially bought this car, I had planned on leaving it stock. The gearhead in me wanted more power and thought "It would be SO cool to make this car fast."

Then I realized "It isn't going to be a fast car" so I started modding it for efficiency and squeezing what I could out of it.

Before I begin let me say I like technical stuff, I love technical data. The mods are easy, short and sweet... but I will also explain why they work, how they work and some bits of info for the curious.

Part 1: INTAKE

The first thing Ford did on this car to make it quieter was the resonators on the intake. For people who are not the technically inclined sort, a resonator dampens the sound off the intake so the car is "quieter". Think of it like a quiet muffler on your exhaust, it muffles the sound and deadens the sound it makes. MANY modern day cars have them. Not all are removable, some are built in. But either way, they are restrictive 90% of the time. This is great and everything, but during stop and go traffic and hot days the zx2 suffers and feels like it's "Suffocating" and you notice it feels like it's just not responsive as much.

There are a few reasons for this.

1. The air that it draws is somewhat warm.
2. It has only one opening in the intake
3. The resonators don't make for extremely efficient airflow through the intake, minimizing power it /could/ have.

Thankfully. There's a fix and it costs only $5-10.

You need a piece of flared pvc piping that is 2.5" diameter with the end being flared to 2 7/8", this is hard to find... and i don't like doing it this way because this this was a popular way of modifying it, but the problem with it is that the pvc piping can warp with extreme heat as well as over time. Causing a leak in the intake (and allowing crap to get into your motor) or not making efficient airflow.

A friend and I tried something different though, it costs more, but it stays the same. If you can find a muffler shop that is /willing/ to try it, have them cut a piece of 2.5" muffler tubing the same length as your upper resonator (bring it in with you). Have them flare the end to the same amount, 2 7/8"

You can do either of these this way, and all you do is put it in your intake where your upper resonator was. now you have no more upper resonator, better airflow, more power, more efficiency.

The other half of this is to remove the LOWER resonator, it literally looks like a giant milk jug. It will free up another hole in the tip of the intake. Your car will get a little more air when it needs it, that "Starving" feeling goes away, a bit more power once again.

If you want to go the extra mile put a K&N drop in filter to replace the old filter.

Overall you get a bit more power, more efficiency, better mileage and the car responds better. getting rid of the lower resonator also makes a bit more room in the well of the engine bay so it doesn't pull in /as/ much hot air

------------Part 2: Weight

The car is pretty light. But of course any weight you can lose is less strain to get the car to accelerate, freeing up power you already have.

Here's why. Ford added lots of sheet metal pieces to parts of the interior for some weird reasons. The glove box for one has a GIANT HEAVY piece of metal inside the door for it to help it "drop". You can literally press in the plastic pins on the inside, use a philips screwdriver to take apart the "glove compartment door" pull the metal out, and put it back together. Your door drops just as well without the heavy *CLUNK* when it opens, you lost 5 lbs.

The stereo deck is insanely heavy from ford. The premium system uses a 6 cd changer and a super heavy setup. The cd changer, stock deck and stock speakers alone were probably a good 40-50lbs or so (no joke). An aftermarket cd player in the dash and regular aftermarket speaker setup and I had lost a good amount of weight and it sounded better (hey, you can't hate that). alternatively, you don't /have/ to replace the speakers, but removing the cd changer, the brackets, the bolts, the OEM stereo deck all in it's own is a gain. (this costs a little, so i realize some people may not be interested).

The trunk has a small pressed board cover that goes over your spare tire. The point of this is to support anything up on top of it. If you don't carry huge loads in your trunk you can cut a piece of pegboard and put it in it's place (less weight), or a piece of aluminum sheet metal (much lighter) or alternatively take it out altogether. There are 2 of these, one that covers your jack for your spare tire and the giant piece that goes over the spare tire itself.

If you want to get even more nutty, another modification to free up even more weight is an aftermarket crank pulley. I did this to make more power and for weight both. It really doesn't pay off till longterm because it costs around $100 for the kit (if you do it yourself) but dyno'd in is an extra 5hp (no joke) freed up because the stock crank pulley is INSANELY heavy, probably a good 10-20lbs. The underdrive pulley weighs far less, probably 1lb or less. The good thing about this too is that because it is underdriving your accessories this means it will still function just fine, it isn't so under-driven that your battery refuses to charge or has a problem charging and your alternator will last LONGER as it isn't going through as many rotations over the course of time. Increase in efficiency, alternator life, more power? Good.

On top of this, if you really feel like getting gutsy you can get a bypass pulley out of a junk yard from a zx2 that didn't come with A/C, or order one and then take out the A/C. Huge weight savings, less drag on your pulley system, more power, more efficiency, more MPG. For those that live in an extremely hot area, this may not be an option as I realize windows down on the highway vs AC is both going to lower it. I use neither.

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Part 3: Driving tips for the Z

Shifting - This car can sometimes be a PITA in 1st and 2nd gear in downshifts. There is a trick to this that is really easy on your synchros. Now this has little to do with mileage, and more to do with making your tranny last longer (which in these cars if they are mistreated DO NOT last long).

When you are downshifting from 3rd into second, do so when the car is at about 1500-2000 rpms and as the rpms are dropping/winding down. Or push in the clutch, put it in neutral, push in the clutch again and slowly match the rpms. It should smoooooothly engage into gear.

From 2nd to 1st do it at a CRAWL. If you are still moving even at 5mph you can still leave it in 2nd, try not to downshift into 1st if you don't have to if you are still moving, you'll hear it wind to try and match up with the synchros. Instead, when you are nearly at a stop, just before you are entirely stopped, crawling, slowly stick it in 1st, it should slide into gear with no resistance.

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Some of these concepts remain the same on other vehicles too. Like I said. Many cars have resonators on their intakes, if they can be modified or removed it can make it more efficient, making more power available to you on the highway. I like K&N filters because you aren't buying a new filter every season, you save money longterm and it does help a little on power, which every bit helps for the highway.

Any kind of weight reduction can help, remember most car companies add some things that are there for "convenience" and not necessarily always efficiency (heavy parts that don't need to be there, stuff you don't use, etc).

I would recommend measuring the pressure drop with a manometer before removing the intake reasonators to see if thats the real problem. Driving like we do, for fuel economy, we almost never run into restrictions in the intake or exhaust simply because we avoid high rpms.

I would recommend measuring the pressure drop with a manometer before removing the intake reasonators to see if thats the real problem. Driving like we do, for fuel economy, we almost never run into restrictions in the intake or exhaust simply because we avoid high rpms.

Good point. I unfortunately do not have such a tool. Nor do I understand that... but I will google it and see if I can learn more about what you are talking about But that's a valid point you make. My main concern wasn't really more power at high rpms, but rather that it felt "boggy", slow to respond and what not when it got hot outside, especially in stop and go traffic, and this seemed to help a little.

A manometer is really just a pressure gauge, but it can reference two pressures to show the difference in pressure (pressure differential). You put one end of it before the resonator section and the other end after the resonator section. You would then go for a drive in the car and make a few passes at wide open throttle (WOT). You can see at what RPM the resonator section actually starts to create a pressure drop (power loss). The larger the pressure drop the more power you've lost. However, if there is no noticable pressure differential until say 5000 rpm, your not gaining anything by removing it until you go over 5000 rpm. If your driving to get the best mileage you shouldn't be anywhere near 5k rpm.

A manometer is really just a pressure gauge, but it can reference two pressures to show the difference in pressure (pressure differential). You put one end of it before the resonator section and the other end after the resonator section. You would then go for a drive in the car and make a few passes at wide open throttle (WOT). You can see at what RPM the resonator section actually starts to create a pressure drop (power loss). The larger the pressure drop the more power you've lost. However, if there is no noticable pressure differential until say 5000 rpm, your not gaining anything by removing it until you go over 5000 rpm. If your driving to get the best mileage you shouldn't be anywhere near 5k rpm.

Here is a rough pic:

Haha, very true! That's good information though, thank you for that bit of wisdom. Much appreciated

You're right, this car pretty much NEVER sees that. It sees 2700-2900rpms maximum, daily and that's on the highway.

Right now i'm between 30-35mpg (around what you're getting), i have pretty decent amount of in town driving in the morning though.

Thanks to this site though, I'll be changing those and we'll see what kind of mileage I get now I need to get one of those plug in trackers everyone has been talking about to see my solid numbers.

You are lucky you have a 98'. They had slightly shorter gearing in 1998 and the transmissions were actually stronger, in 1999.5 (the early 99 was basically the same) they moved up to new internals and went off of more mazda parts, in fact, I think it's technically a mazda transmission. If you take care of it then it should last a very long time.

I changed jobs recently and lost my company car, so I had to find something to replace it. I found a really clean 1999 ZX2 with only 60,000 miles on it and bought it for $4,500 out the door. It is a 5 speed manual, basic model, no frills. When I first started checking my gas mileage, I was getting about 35mpg per fillup. I then discovered this site and gassavers.org, and started trying to improve my FE. By changing my driving habits, I was able to increase my mileage to 38mpg per fillup. I then decided to do some mods, and not spend any money. First I inflated my tires to 10% over max and was able to get 39mpg. Then I did my version of the Keman intake mod and this put me over 41mpg. I just installed the IAT resistor and disconnected the knock sensor, and will see what happens on this tank. Disconnecting the knock sensor really made a difference in the smoothness of the engine. No more hesitation when taking off from a stop, better shifts. All I have spent so far is .99 cents for the resistor pack of 5 at Radio Shack. If it does'nt work, so what.

For the intake mod, I removed the lower resonator and cut the airbox around the air filter like the "normal" Keman mod. Still running the stock air filter. On the upper resonator, I removed it and just cut off the square box on the side of the tube and removed the white plastic grid with the holes in it from the inside. Then I smoothed out the projections on the outside of the grid and installed it on the outside of the tube over the hole where the square box was cut off. I sealed it with aluminum duct tape and put black duct tape over that. Reinstalled the tube in the original location and so far so good. I keep an eye on it, as I know the heat may be a problem with the tape. But it cost a total of 0 dollars. This mod was great as I really can feel the difference in the low end and throttle response.

I am having fun watching my FE increase as I do small things and with no investment other than time, any increase is $ in my pocket. I can't see spending $169.00 on a Scangauge II, as that would put me in the hole, so to speak.

It's nice to see that you all are getting good results with the ZX2. I have always thought it was a beautiful car, but never thought it would do so well. Please, keep it coming. I may have to try to find one myself sometime.